In recent years, the use of electromagnetic waves in the range of millimeter waves (with a wavelength on the order of 1 to 10 mm and a frequency of 30 to 300 GHz) and submillimeter waves as an information communication medium has been on the increase. In the field of motor vehicle technology, the use of electromagnetic waves has been on the increase, for example, in collision avoidance systems which automatically apply brakes upon sensing obstacles and which measure the speed of a neighboring vehicle and a distance between a user's vehicle and the neighboring vehicle to control the speed of the user's vehicle and the distance between the vehicles. For normal operation of such systems, it is important to receive as little unwanted electromagnetic wave radiation as possible in order to prevent false recognition. It is hence desirable to use electromagnetic wave absorbers that absorb unwanted electromagnetic waves for the purpose of ensuring the performance of these systems.
The aforementioned electromagnetic wave absorbers are of various types according to the principles of the absorption of the electromagnetic waves. For example, it is known that an electromagnetic wave absorber of the type (referred to hereinafter as a “λ/4 type”) including an electromagnetic wave reflection layer, a dielectric layer having a thickness of λ/4 (where λ is an intended wavelength of an electromagnetic wave) and a resistive thin film layer is produced at low costs because of its relatively inexpensive materials and its easier designs. An electromagnetic wave absorber having an excellent property of functioning over a wide range of incident angles has been proposed in PTL 1, for example, as such a λ/4 type electromagnetic wave absorber.